Secondary containment systems at gasoline service stations are commonly used in order to contain any leakage from the underground piping associated with such service stations. A typical service station includes a number of underground product tanks which contain the different grades of fuel sold and a number of different product dispensers for dispensing the products to customers. Product pumps, typically one associated with each product tank, are located at the respective product tanks and feed the various products to the dispensers through underground product conduits.
As the first component of a typical secondary containment system, product tanks are provided of a double-walled construction so that any leakage from the tank will be contained and will not contaminate the surrounding soil. Such secondary containment systems also include double walled product conduits, similarly intended to contain any product leakage from the product conduits and prevent contamination.
A typical secondary containment system further includes a number of underground containment boxes which house the piping connections between the product tanks and the product conduits as well as between the product conduits and product dispensers. A first group of containment boxes are located at each product tank. The product pumps are generally located within these containment boxes. These containment boxes provide access to the product pumps for maintenance purposes and are also intended to contain any product that may spill from the product pumps or their associated piping.
A second group of containment boxes are located under each product dispenser or group of product dispensers. These containment boxes house the necessary piping connections and fittings that connect the product lines to the dispensers and contain any product that may spill from the dispenser or its associated piping.
At the low points of such secondary containment piping systems, liquid sensors are often used so as to monitor whether any leakage has occurred from the system. Such sensors can be used to either sound an alarm or shut down equipment as necessary to prevent further spillage. Some examples of the various components used in secondary containment systems can be found in U.S. Pat. No. 4,842,163 which is hereby incorporated by reference.